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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 433 records · Page 24
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NASA NTRS1988

Drag measurements on a body of revolution in Langley's 13-inch Magnetic Suspension and Balance System

NASA Langley's 13-inch Magnetic Suspension and Balance System (MSBS) has been used to conduct low-speed wind tunnel drag force measurements on a laminar-flow body-of-revolution free of support system interference, in order to verify the drag force measurement capabilities of the MSBS. The drag force calibrations and wind-on repeatability data obtained have verified the design capabilities for this system. A drag-prediction code has been used to assess the MSBS's usefulness in body drag estimation.

Dress, David A.↗
NASA NTRS1987

Fluid dynamics parallel computer development at NASA Langley Research Center

To accomplish more detailed simulations of highly complex flows, such as the transition to turbulence, fluid dynamics research requires computers much more powerful than any available today. Only parallel processing on multiple-processor computers offers hope for achieving the required effective speeds. Looking ahead to the use of these machines, the fluid dynamicist faces three issues: algorithm development for near-term parallel computers, architecture development for future computer power increases, and assessment of possible advantages of special purpose designs. Two projects at NASA Langley address these issues. Software development and algorithm exploration is being done on the FLEX/32 Parallel Processing Research Computer. New architecture features are being explored in the special purpose hardware design of the Navier-Stokes Computer. These projects are complementary and are producing promising results.

Townsend, James C.↗
NASA NTRS1987

Turbulent drag reduction research at NASA Langley - Progress and plans

Prospective research efforts planned at NASA-Langley in view of results obtained to date in passive turbulent drag reduction experiments are discussed. It has been established that conventional flow-aligned riblets are effective even in the presence of a degree of flow inclination and pressure gradients, and at transonic speeds. No increase in net drag reduction is expected from nonconventional riblet geometries. Large eddy breakup devices promise drag reductions in the 8-15 percent range. Heat transfer-augmentation, noise-reduction, turboprop/fuselage interaction noise reduction, are other advantages expected from this line of research.

Wilkinson, S. P.↗
NASA NTRS1988

Experimental results for the Eppler 387 airfoil at low Reynolds numbers in the Langley low-turbulence pressure tunnel

Experimental results were obtained for an Eppler 387 airfoil in the Langley Low Turbulence Pressure Tunnel. The tests were conducted over a Mach number range from 0.03 to 0.13 and a chord Reynolds number range for 60,000 to 460,000. Lift and pitching moment data were obtained from airfoil surface pressure measurements and drag data for wake surveys. Oil flow visualization was used to determine laminar separation and turbulent reattachment locations. Comparisons of these results with data on the Eppler 387 airfoil from two other facilities as well as the Eppler airfoil code are included.

Mcghee, Robert J.↗
NASA NTRS1988

Sidewall boundary-layer measurements with upstream suction in the Langley 0.3-meter transonic cryogenic tunnel

The Langley 0.3 Meter Transonic Cryogenic Tunnel has provision for boundary removal from the sidewalls to reduce sidewall interference effects on the test data. The tests carried out to determine the change in the empty test section sidewall boundary layer thickness at the model station with upstream boundary layer mass removal are described. The boundary layer measurements showed that the upstream removal region is effective in reducing the boundary layer thickness at the model station. The boundary layer displacement thickness reduced from about 1.2 percent to about .4 percent of the test section width. The boundary layer velocity profiles followed a power law variation in the outer region and showed good correlation when plotted in terms of boundary layer momentum thickness.

Murthy, A. V.↗
NASA NTRS1988

Wall adjustment strategy software for use with the NASA Langley 0.3-meter transonic cryogenic tunnel adaptive wall test section

The Wall Adjustment Strategy (WAS) software provides successful on-line control of the 2-D flexible walled test section of the Langley 0.3-m Transonic Cryogenic Tunnel. This software package allows the level of operator intervention to be regulated as necessary for research and production type 2-D testing using and Adaptive Wall Test Section (AWTS). The software is designed to accept modification for future requirements, such as 3-D testing, with a minimum of complexity. The WAS software described is an attempt to provide a user friendly package which could be used to control any flexible walled AWTS. Control system constraints influence the details of data transfer, not the data type. Then this entire software package could be used in different control systems, if suitable interface software is available. A complete overview of the software highlights the data flow paths, the modular architecture of the software and the various operating and analysis modes available. A detailed description of the software modules includes listings of the code. A user's manual is provided to explain task generation, operating environment, user options and what to expect at execution.

Wolf, Stephen W. D.↗
NASA NTRS1989

NASA SC(2)-0714 airfoil data corrected for sidewall boundary-layer effects in the Langley 0.3-meter transonic cryogenic tunnel

This report presents the corrected aerodynamic data for A NASA SC(2)-0714 airfoil tested in the Langley 0.3-Meter Transonic Cryogenic Tunnel. This test was another in the series of tests involved in the joint NASA/U.S. industry Advanced Technology Airfoil Tests program. This 14 percent thick critical airfoil was tested at Mach numbers from 0.6 to 0.76 and angles of attack from -2.0 to 6.0 deg. The test Reynolds numbers were 4 million, 6 million, 10 million, 15 million, 30 million, 40 million, and 45 million. Corrections for the effects of the sidewall boundary layer have been made. The uncorrected data were previously published in NASA Technical Memorandum 4044.

Jenkins, Renaldo V.↗
NASA NTRS1989

The NASA Langley laminar-flow-control experiment on a swept, supercritical airfoil - Drag equations

The Langley Research Center has designed a swept, supercritical airfoil incorporating Laminar Flow Control for testing at transonic speeds. Analytical expressions have been developed and an evaluation made of the experimental section drag, composed of suction drag and wake drag, using theoretical design information and experimental data. The analysis shows that, although the sweep-induced boundary-layer crossflow influence on the wake drag is too large to be ignored and there is not a practical method for evaluating these crossflow effects on the experimental wake data, the conventional unswept 2-D wake-drag computation used in the reduction of the experimental data is at worst 10 percent too high.

Brooks, Cuyler W., Jr.↗
NASA NTRS1989

Performance of the active sidewall boundary-layer removal system for the Langley 0.3-meter Transonic Cryogenic Tunnel

A performance evaluation of an active sidewall boundary-layer removal system for the Langley 0.3-m Transonic Cryogenic Tunnel (TCT) was evaluated in 1988. This system uses a compressor and two throttling digital valves to control the boundary-layer mass flow removal from the tunnel. The compressor operates near the maximum pressure ratio for all conditions. The system uses a surge prevention and flow recirculation scheme. A microprocessor based controller is used to provide the necessary mass flow and compressor pressure ratio control. Initial tests on the system indicated problems in realizing smooth mass flow control while running the compressor at high speed and high pressure ratios. An alternate method has been conceived to realize boundary-layer mass flow control which avoids the recirculation of the compressor mass flow and operation near the compressor surge point. This scheme is based on varying the speed of the compressor for a sufficient pressure ratio to provide needed mass flow removal. The system has a mass flow removal capability of about 10 percent of test section flow at M = 0.3 and 4 percent at M = 0.8. The system performance has been evaluated in the form of the compressor map, and compressor tunnel interface characteristics covering most of the 0.3-m TCT operational envelope.

Balakrishna, S.↗
NASA NTRS1989

The NASA Langley Laminar-Flow-Control Experiment on a Swept Supercritical Airfoil: Basic Results for Slotted Configuration

The effects of Mach number and Reynolds number on the experimental surface pressure distributions and transition patterns for a large chord, swept supercritical airfoil incorporating an active Laminar Flow Control suction system with spanwise slots are presented. The experiment was conducted in the Langley 8 foot Transonic Pressure Tunnel. Also included is a discussion of the influence of model/tunnel liner interactions on the airfoil pressure distribution. Mach number was varied from 0.40 to 0.82 at two chord Reynolds numbers, 10 and 20 x 1,000,000, and Reynolds number was varied from 10 to 20 x 1,000,000 at the design Mach number.

Harris, Charles D.↗
NASA NTRS1989

Microcomputer based controller for the Langley 0.3-meter Transonic Cryogenic Tunnel

Flow control of the Langley 0.3-meter Transonic Cryogenic Tunnel (TCT) is a multivariable nonlinear control problem. Globally stable control laws were generated to hold tunnel conditions in the presence of geometrical disturbances in the test section and precisely control the tunnel states for small and large set point changes. The control laws are mechanized as four inner control loops for tunnel pressure, temperature, fan speed, and liquid nitrogen supply pressure, and two outer loops for Mach number and Reynolds number. These integrated control laws have been mechanized on a 16-bit microcomputer working on DOS. This document details the model of the 0.3-m TCT, control laws, microcomputer realization, and its performance. The tunnel closed loop responses to small and large set point changes were presented. The controller incorporates safe thermal management of the tunnel cooldown based on thermal restrictions. The controller was shown to provide control of temperature to + or - 0.2K, pressure to + or - 0.07 psia, and Mach number to + or - 0.002 of a given set point during aerodynamic data acquisition in the presence of intrusive geometrical changes like flexwall movement, angle-of-attack changes, and drag rake traverse. The controller also provides a new feature of Reynolds number control. The controller provides a safe, reliable, and economical control of the 0.3-m TCT.

Balakrishna, S.↗
NASA NTRS1989

Recent activities within the Aeroservoelasticity Branch at the NASA Langley Research Center

The objective of research in aeroservoelasticity at the NASA Langley Research Center is to enhance the modeling, analysis, and multidisciplinary design methodologies for obtaining multifunction digital control systems for application to flexible flight vehicles. Recent accomplishments are discussed, and a status report on current activities within the Aeroservoelasticity Branch is presented. In the area of modeling, improvements to the Minimum-State Method of approximating unsteady aerodynamics are shown to provide precise, low-order aeroservoelastic models for design and simulation activities. Analytical methods based on Matched Filter Theory and Random Process Theory to provide efficient and direct predictions of the critical gust profile and the time-correlated gust loads for linear structural design considerations are also discussed. Two research projects leading towards improved design methodology are summarized. The first program is developing an integrated structure/control design capability based on hierarchical problem decomposition, multilevel optimization and analytical sensitivities. The second program provides procedures for obtaining low-order, robust digital control laws for aeroelastic applications. In terms of methodology validation and application the current activities associated with the Active Flexible Wing project are reviewed.

Noll, Thomas E.↗
NASA NTRS1989

Overview of Dynamics Integration Research (DIR) program at Langley Research Center

Research goals and objectives for an ongoing activity at Langley Research Center (LaRC) are described. The activity is aimed principally at dynamics optimization for aircraft. The effort involves active participation by the Flight Systems, Structures, and Electronics directorates at LaRC. The Functional Integration Technology (FIT) team has been pursuing related goals since 1985. A prime goal has been the integration and optimization of vehicle dynamics through collaboration at the basic principles or equation level. Some significant technical progress has been accomplished since then and is reflected here. An augmentation for this activity, Dynamics Integration Research (DIR), has been proposed to NASA Headquarters and is being considered for funding in FY 1990 or FY 1991.

Sliwa, Steven M.↗
NASA NTRS1989

Langley rotorcraft structural dynamics program: Background, status, accomplishments, plans

Excessive vibration is the most common technical problem to arise as a show stopper in the development of a new rotorcraft. Vibration predictions have not been relied on by the industry during design because of deficiencies in finite element dynamic analyses. A rotorcraft structural dynamics program aimed at meeting the industry's long-term needs in this key technical area was implemented at Langley in 1984. The subject program is a cooperative effort involving NASA, the Army, academia, and the helicopter industry in a series of generic research activities directed at establishing the critical elements of the technology base needed for development of a superior finite element dynamics design analysis capability in the U.S. helicopter industry. An executive overview of the background, status, accomplishments, and future direction of this program is presented.

Kvaternik, Raymond G.↗
NASA NTRS1988

Langley Research Center resources and needs for manned space operations simulation

This paper describes current simulation research activities carried out at the Langley Research Center in the areas of remotely controlled operations, task performance, and analytical operations, along with early simulators developed at the center. Special attention is given to the center's current space simulation capabilities which are applicable to manned space operation studies, including the Advanced Concepts Simulator (ACS) and a computer-generated imagery (CGI). The ACS was designed to represent an aircraft cockpit for flight operations in the 1990s but will be also suitable for simulating a variety of astronaut work station applications. The CGI, scheduled for delivery in 1989, will be able to provide out-the-window scenes representative of many operational tasks from rendezvous and docking/berthing to control of telerobotic devices.

Nunamaker, Robert R.↗
NASA NTRS1988

Advanced Technology Space Station studies at Langley Research Center

The paper describes the Advanced Technology Space Station systems studies at Langley Research Center, which were initiated to identify the technologies required for the construction of a high-performance station in the first quarter of the 21st century. Technologies which would maximize the synergistic effects between the subsystems and structural configurations were selected. The ECLSS and propulsion systems show promising synergistic relationships in the areas of oxygen and hydrogen production and attitude control.

Ferebee, Melvin J., Jr.↗
NASA NTRS1989

Sidewall boundary-layer removal effects on wall adaptation in the Langley 0.3-meter transonic cryogenic tunnel

This paper describes the Langley 0.3-m transonic cryogenic tunnel sidewall boundary-layer removal system and is integrated operation with the adaptive wall adjustment. Empty test section measurements show the sidewall boundary-layer displacement thickness at the model station is reduced from about 1.0 to 0.6 percent of the test section width when the maximum boundary-layer removal conditions are applied. Tests with a supercritical airfoil model show the iterative top and bottom wall adaptation process performs satisfactorily with sidewall boundary-layer removal.

Murthy, A. V.↗
NASA NTRS1988

Results from NASA Langley experimental studies of multiaxis thrust vectoring nozzles

Multiaxis thrust-vectoring nozzles can furnish substantial combat performance gains for military aircraft; in pursuit of these gains, NASA-Langley has conducted an extensive experimental research program encompassing both static and freestream performance evaluations for numerous multiaxis thrust-vectoring nozzle concepts using air-powered simulation models. An evaluation is presently made of a selection of these experimental results. Two-dimensional and axisymmetric convergent-divergent configurations and hybrid configurations, with and without postexit vanes, have been studied.

Berrier, Bobby L.↗